A variety of electronic devices, such as measuring devices, medical monitors or test devices, perform their functions under control of a microprocessor. Although the measurement pickups (e.g., the test probe and input amplifiers of an oscillograph or data bus analyzer, or the electrodes and preamplifiers of a medical monitor) still consist of analog electronics, more complex functions are performed by the microprocessor. Such functions include guiding the user through menus, performing complex mathematical or statistical operations, presenting measurement results with, e.g., special graphics or the like, software filtering (i.e., software processing of data converted from analog to digital format), controlling certain hardware components (such as an amplifier), setting the bandwidth of a hardware filter, controlling an analog-to-digital converter, etc. These examples illustrate that a processor controlling an electronic device performs many complex functions; therefore the programs necessary for the processor are also very extensive and complex.
Implementing such extensive software functions creates new tasks and problems. For example, it is well-known that an extensive program package is seldom completely free of software errors (so-called "bugs"). Although most software manufacturers try to test their programs under many conditions, it is simply impossible to test a program under all possible conditions, particularly conditions which occur very seldom. Therefore, every complex program needs service: whenever a bug is detected, it must be identified and corrected; the corrected program must then be installed in place of the defective program. This is the reason many software suppliers provide so-called "updates" to their programs. In the updated version, the bugs detected up to a certain point in time have been fixed.
Another reason for installing a software update is to add a new feature to the existing software. For example, a new feature could include the support of a new interface, or the capability of communicating with the user in another language. An additional software feature may also be required when an extensive test of the electronic device is to be carried out. Typical monitors and measuring instruments contain one or more test programs (e.g., a self-test of the memory and input/output ports, carried out when power is turned on); however it is not possible or at least not economical to provide test software for all tests, in particular very special tests, in the standard software for most electronic devices. Accordingly, from time to time it is necessary to load special or extensive test programs in such devices.
In the field of large and medium-size computers, these problems are solved in two different ways:
1. In many cases, e.g. if an operating system update is needed, the new or revised program is installed by a service technician. The technician carries the new program(s) to the customer using magnetic media (such as a disc or tape) and loads the program(s) into the computer. This is a feasible solution for larger computers since the cost of a personal visit of the service technician is negligible compared to the value of the whole computer. Moreover, computer software of this size needs service from time to time anyway, so that a regular service visit may be combined with the installation of the software update.
2. If the revision, update or additional program belongs to a less critical environment of the computer (i.e., a program which is not part of or related to the operating system), then the new software may also be sent to the customer on disk or tape and the customer may be asked to install the new software himself or herself.
Unfortunately, these solutions are not suitable or cost-effective for measuring instruments, small computers and the like; the major reason therefore is that the expenses for a service technician's visit are not acceptable when compared to the cost of the overall system. Furthermore, the exchange of programs is often quite complicated from a technical standpoint, since, in most of these devices, the programs are stored in so-called "firmware"; therefore any software change requires that the electronic device be disassembled and certain memory chips (or complete printed circuit boards) be exchanged. Even in cases where the device comprises a disc drive or a magnetic tape unit, part of the software (in particular, the basic loading and input/output routines) is stored in ROM. On the other hand, since exchanging a ROM requires disassembly of the device, the exchange can only be performed by a qualified service technician. Therefore, in regard of the expenses involved, software updates of the kind described here are seldom asked for or provided.
The situation is even more critical in case of medical devices. In all such devices it is absolutely unacceptable to have a software update installed by the customer, as an erroneously-installed update could place a patient in serious danger. For example, even a minor error could cause distortion of an alarm limit so that the medical device will not initiate an alarm when the patient is in a clinically critical condition. Since this could lead to the death of the patient, it cannot be tolerated. As a consequence, software updates incorporating new features are seldom installed in medical devices; if an update is necessary due to detected errors in the existing software, enormous costs must be borne by the manufacturing company and/or customer.